1. Field of the Invention
The present invention relates to image sensing devices, and more particularly to an image sensing device having reduced energy dispersal taking place between adjacent pixels.
2. Description of the Related Art
Image sensing devices are necessary components in many optoelectronic devices, including digital cameras, cellular phones, and toys. Conventional sensing devices include both charge coupled device (CCD) image sensors and complementary metal oxide semiconductor (CMOS) image sensors.
An image sensing device typically includes a plane array of pixel cells, wherein each pixel cell comprises a photogate, a photoconductor or a photodiode having a doped region for accumulating a photo-generated charge. A periodic pattern of dyes of different colors such as red (R), green (G), or blue (B) is superimposed over the plane array of pixel cells. This pattern is known as a color filter array (CFA). A plurality of microlenses of a square or a circular shape can be optionally superimposed over the color filter array (CFA) to focus light onto one initial charge accumulation region of each of the pixel cells. Using the microlenses may significantly improve the photosensitivity of the image sensor.
However, due to the trend of reducing the size of the pixel cells in image sensing devices, the energy (i.e. electromagnetic wave) of incident light passes through the microlens and focuses at the center of one of the pixels, which may thus disperse or refract into a pixel adjacent thereto, thereby causing a malfunction and a reduction of the sensitivity of the pixel cells in the image sensing device.